Detective Chief Inspector Mark Cranwell told the New Journal there were “issues between several gangs”, but he was keeping an open mind on a possible motive.

A music video, uploaded to the web days before Calvin’s murder, is forming part of the inquiry. DCI Cranwell said some of the language used appeared to be trying to “goad” another gang.

He called on a group of “young, black males” who were with Calvin before his murder to get in touch with police or to contact them anonymously.

A team of 25 detectives working on the case is trying to trace a “key witness” in a dark-coloured car who was reversing away from the scene just seconds before the attack.

As the inquiry enters its second week, officers believe the suspects ran out of Vicar’s Road and chased Calvin down Grafton Road before killing him. They then ran back into Vicar’s Road, got into a car and drove off in the direction of Weedington Road.

Witnesses have told police the suspects have black and white ethnicities.

Police believe the car was found burnt out the day after the killing. They are appealing for a phone belonging to Calvin to be handed in. It is believed to have been removed from the scene of the murder.

Calvin grew up in the Denton block of flats in Kentish Town. He was a pupil at St Dominic’s Catholic Primary School before going to Haverstock. His family were grieving nearly exactly a year ago when his father died.

Mr Mampuila said: “It’s very sad for the family. Calvin was funny, he was always laughing, he was a very good boy.”

Key witness: police are keen to trace the driver of this dark coloured car which was seen reversing away from the scene seconds before the attack

Chief Superintendent Raj Kohli, the new borough commander, told the meeting on Tuesday: “In terms of Calvin’s death, investigations go on. It’s fair to say the team investigating it are frustrated. They don’t appear to have names of the people involved. I hear a lot about people not talking to police about what they know, or thinking what they know is not relevant, but everything you know is relevant. Not talking to us doesn’t get justice for Calvin and his family.

He added: “My plea is talk to us, tell us what you know. Tell us anonymously. Let us at least get some justice for Calvin and perhaps stop something like this happening again.”